Microorganism for breaking down moenomycins, a process for the breakdown, and the use of the breakdown products

ABSTRACT

A new microorganism for breaking down moenomycins, a process for the breakdown, and the use of the breakdown products are disclosed. A new Bacillus species and the appropriate enzymes obtained therefrom can be used to break down phosphoglycolipid antibiotics. The breakdown products of moenomycins display antibiotic activity or can be used as building blocks for the synthetic preparation of transglycosylase inhibitors.

This is a continuation-in-part application of application Ser. No. 07/927,886, filed Aug. 11, 1992, now U.S. Pat. No. 5,206,405, which is a continuation of application Ser. No. 07/617,635, filed Nov. 26, 1990, now abandoned, which is a division of application Ser. No. 07/395,790, filed Aug. 18, 1989, now abandoned, and is also a continuation-in-part of copending application Ser. No. 07/938,599, filed Sep. 3, 1992, now U.S. Pat. No. 5,260,206, which is incorporated herein by reference, which is a continuation-in-part of application Ser. No. 07/762,262, filed Sep. 20, 1991, now abandoned, which is a continuation of application Ser. No. 07/711,708, filed Jun. 7, 1991, now abandoned, which is a continuation of application Ser. No. 07/395,790, filed Aug. 18, 1989, now abandoned.

Moenomycin A is the main component of Flavomycin® which is used in livestock nutrition. Like other known phosphoglycolipid antibiotics it inhibits the biosynthesis of the peptidoglycan framework of the bacterial cell wall. Closer investigations showed that the transglycosylation reaction of the penicillin-binding protein 1b of E. coli is inhibited by these substances (G. Huber, in F. E. Hahn (ed.) Antibiotics, Vol. 1, 135-153, Berlin: Springer, 1979). Attempts at specific enzymatic or microbial breakdown of phosphoglycolipid antibiotics have hitherto failed.

Several attempts to chemically synthesize biologically active structural analogues of the moenomycin-type antibiotics have been unsuccessful.

H. Hohgardt et al., Tetrahedron, 44(18):5771-5790 (1988), were able to prepare disaccharides connected via phosphorous acid and glycerol acid to the saturated moenocinol. These compounds were devoid of any antibiotic activity. They differ from an active disaccharide moenomycin analogue (prepared from moenomycin by chemical degradation as described in P. Welzel et al., Tetrahedron, 43:585-598 (1987)), in (1) having a galacturonic acid configuration instead of a moenuronic acid configuration, (2) lacking double bonds in the lipid (alkyl) moiety, and (3) bearing a carboxylic acid at position 6 of moenuronic acid rather than a carboxamide.

U. Moller et al., Tetrahedron, 49:1635-1648 (1993)), introduced the missing carboxamide into the substructure at position 6 of moenuronic acid, resulting in a molecule which differs from an active analogue only in (1) having a galacturonic acid configuration instead of a moenuronic acid configuration, and (2) lacking double bonds in the alkyl chain. Surprisingly, this compound was also antibiotically inactive.

Surprisingly, a new Bacillus species which is able to cleave the phosphoglycolipid antibiotics to defined end products has now been isolated from a contaminated fermenter for the preparation of flavomycin using Streptomyces ghanaensis. These end products have antibiotic activity or can be used as building blocks in the synthesis of new transglycosylase inhibitors.

Hence, the invention relates to:

1. Bacillus spec. DSM 4675 and the variants and mutants thereof.

2. The cleavage product of moenomycin A with the formula I. ##STR1## 3. The cleavage product of the phosphoglycolipid antibiotics with the general formula ##STR2## in which R¹ is hydrogen or a phosphono group [--PO(OH)₂ ] and R² is a (C₅ to C₅₅)-alkyl group which can be branched or unbranched, saturated or unsaturated.

4. The enzymes with whose aid the phosphoglycolipid antibiotics can be cleaved at the phosphoglycosidic linkage, or the cleavage products specified under 3. can be cleaved at the monophosphate ester linkage.

5. A process for the preparation of the breakdown products specified under 2. and 3., which comprises incubating phosphoglycolipid antibiotics with Bacillus spec. DSM 4675.

6. The use of the substances specified under 2. and 3. as building block for the synthetic preparation of transglycosylase inhibitors or as substance having antibiotic activity.

The invention will be described in detail hereinafter, especially in the preferred embodiments. It is furthermore defined in the claims.

Bacillus spec. was deposited with the number DSM 4675 under the provisions of the Budapest Treaty at the Deutsche Sammlung von Mikroorganismen und Zellkulturen GmbH (German Microorganism and Cell Culture Collection) in Braunschweig, FRG, on Jun. 23, 1988. The characteristics of the strain may be said to be the following:

1. Taxonomic properties of Bacillus sp. DSM 4675

A) Morphology

motile rods; up to 5 μm long; some in short chains

terminal spore; sporangium swollen

Gram-positive.

B) Growth on various media (28° C.; 48 hours)

1. Antibiotic medium 3 (Difco)

rough, lobed colonies of diameter 1-2 mm

2. Luria broth (Bacto tryptone 10 g/l; Bacto yeast 5 g/l; NaCl 5 g/l)

smooth, glossy round colonies of diameter 2-3 mm; opaque

3. Nutrient broth (Difco)

white, glossy colonies with irregular margin

4. Christensen urea agar (Difco)

growth positive

5. McConkey agar (Difco)

growth positive

6. BROLAC agar (lactose) (Difco)

growth positive

7. Simmons citrate agar (Difco)

growth negative

8. No growth in the presence of 7 or 10% NaCl in a peptone/meat extract medium (Difco)

C) Physiological properties

    ______________________________________                                         1.      Oxidase           +                                                    2.      Catalase          +                                                    3.      Hemolysis         -                                                    4.      Aminopeptidase    -                                                    5.      Nitrate reduction -                                                    6.      Phenylalanine deaminase                                                                          -                                                    7.      Growth at                                                                      30° C.     +                                                            40° C.     +                                                            50° C.     +                                                    8.      Anaerobic growth                                                               solid             -                                                            liquid            -                                                    9.      Gas formation from glucose                                                                       -                                                    10.     Indole formation  -                                                    11.     Arginine dihydrase                                                                               -                                                    12.     Urea breakdown    -                                                    13.     Esculin hydrolysis                                                                               +                                                    14.     Gelatin breakdown -                                                    15.     β-Galactosidase                                                                             +                                                    16.     Lysine decarboxylase                                                                             -                                                    17.     Ornithine decarboxylase                                                                          -                                                    18.     H.sub.2 S production                                                                             -                                                    19.     Tryptophan deaminase                                                                             -                                                    20.     Alkal. phosphatase                                                                               -                                                    21.     Voges-Proskauer reaction                                                                         -                                                    ______________________________________                                    

D) Fermentation of carbohydrates

    ______________________________________                                         C source        Assimilation                                                                              Acid formation                                      ______________________________________                                         Adipate         -                                                              Adonitol        -                                                              Arabinose       +          +                                                   Caprate         -                                                              Citrate         -                                                              Dulcitol        -                                                              Fructose        +          +                                                   Galactose       -                                                              Gluconate       +                                                              Glucose         +          +                                                   Inositol        -                                                              Lactose         +          +                                                   Malate          -                                                              Malonate        -                                                              Maltose         +          +                                                   Mannitol        +          +                                                   Mannose         +          +                                                   Melibiose       +          +                                                   Phenylacetate   -                                                              Raffinose       +          +                                                   Rhamnose        -                                                              Sucrose         +          +                                                   Salicin         -                                                              Sorbitol        -                                                              Trehalose       +          +                                                   Xylitol         -          -                                                   Xylose          +          +                                                   N-Acetyl-glucosamine                                                                           -          +                                                   ______________________________________                                    

Taking account of taxonomic features and with the aid of "Bergey's Manual of Systematic Bacteriology" (Vol. 2, Williams and Wilkins publ., Baltimore, 1986) the strain can be assigned to the genus Bacillus. To determine the species, parallel comparative examinations of type cultures of Bacillus macerans, circulans, lentus, alcalophilus, stearothermophilus, licheniformis, polymyxa and fastidiosus were carried out. All the comparison strains showed distinct differences from Bacillus spec. DSM 4675. Nor were any of these strains able to break down phosphoglycolipid antibiotics, especially moenomycin A. The conclusion to be drawn from this is that the strain DSM 4675 is a new species.

The invention also relates in each case to the mutants and variants which, as is known, may arise spontaneously or be generated by treatment with physical agents, for example irradiation, such as ultraviolet or X-rays, or with chemical mutagens such as, for example, ethyl methanesulfonate (EMS), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or 2-hydroxy-4-methoxy-benzophenone (MOB).

Suitable and preferred as carbon source for the aerobic fermentation of Bacillus spec. DSM 4675 are assimilable carbohydrates and sugar alcohols, such as glucose, lactose or mannitol, as well as carbohydrate-containing natural products such as malt extract. Suitable and preferred nitrogen-containing nutrients are: amino acids, peptides and proteins, as well as the breakdown products thereof, such as peptone or tryptone, furthermore meat extracts, milled seeds, for example of corn, beans, soybean or the cotton plant, disillation residues from the production of alcohol, meat meals or yeast extracts, as well as ammonium salts and nitrates. The nutrient solution may additionally contain, for example, chlorides, carbonates, sulfates or phosphates of the alkali metals or alkaline earth metals, iron, zinc and manganese as additional inorganic salts.

The growth of the microorganism and the formation of the enzymes necessary for the breakdown reactions according to the invention is particularly good in a nutrient medium containing corn starch, soybean meal, sucrose, glycerol, peptone and/or corn steep as carbon and nitrogen sources.

The fermentation is carried out aerobically, that is to say, for example, submerged with shaking or stirring in shaken flasks or fermenters, where appropriate introducing air or oxygen. The fermentation can take place in a temperature range from approximately room temperature to 50° C., preferably at about 35° to 37° C. The culturing time is generally 24 to 48 hours.

The cultures of Bacillus DSM 4675 obtained in this way, or preparations thereof, can be used to cleave the phosphoglycolipid antibiotics. These include, in particular, the antibiotics of the moenomycin group, for example pholipomycin¹), the prasinomycins²), the diumycins (macarbomycins)³) esanchomycin, prenomycin and teichomycin, and other structurally related substances which have a correspondingly functionalized phosphoglyceric acid

The enzymes are particularly preferably used to break down the moenomycins, for example Flavomycin.

When Bacillus cells are used it is advantageous to permeabilize the latter, for example with cetyltrimethylammonium salts. It is likewise possible to use protein isolates from the Bacillus cells, or enzyme extracts which have been partially enriched, for example, by salting-out or chromatography or, of course, the purified enzyme. It is furthermore possible to employ the enzyme and cells in free or immobilized form.

The enzymatic breakdown is depicted in the following diagram using moenomycin A as an example. ##STR3##

It is evident from this diagram that two enzymes are needed to prepare the cleavage products. An enzyme, which the inventors have called moenomycinase, is required to cleave the phosphoglycosidic linkage. Moenomycinase is associated with the cytoplasmic membrane of Bacillus spec. DSM 4675 and can be obtained from the microorganism by enzyme isolation methods known per se.

For example, moenomycinase bound to membranes of Bacillus spec. DSM 4675 can be solubilized with the detergent Triton X-100 (1-3%) as described in Example 2A. Moenomycinase can also be isolated without the use of detergent by extensive ultrasound sonication. For example, cells suspended in buffer (20 mM potassium phosphate, pH 8.0, with 0.1 mM CoCl₂) were sonicated for 1-2 minutes. After centrifugation at 20 min×20,000 g, 50-60% of the enzyme activity was found in the supernatant. Alternatively, some activity can be solubilized with cetyltrimethylammonium salts. For example, when cells were incubated (1 g/2 ml) in 0.1% cetyltrimethylammonium salts (0.1%), 10% of the enzyme activity was found in the supernatant after centrifugation for 20 min×20,000 g.

The molecular weight of moenomycinase is 230,000±10,000 Dalton. Moenomycinase is activated by Co⁺⁺, Ni⁺⁺, Mn⁺⁺, Ca⁺⁺ and Mg⁺⁺, and can be inhibited by formalin, EDTA, Cephalosporin C, and 7-aminocephalosporin acid (7-ACA).

Moenomycinase has a pH optimum of about 8.0-8.5, in particular 8.2-8.3. The temperature optimum of the enzyme is 45°-55° C., in particular 49°-51° C. Moenomycinase has a K_(m) value for moenomycin A of 4-10 millimolar.

Two cleavage products are obtained. Cleavage product I comprises the sugar component of the phosphoglycolipid antibiotics. Also obtained is the cleavage product with the general formula II ##STR4## in which R¹ is a phosphono group and R² is a (C₅ to C₅₅)-alkyl group, preferably a (C₁₀ to C₃₀)-alkyl group, in particular a (C₂₀ to C₂₅)-alkyl, each of which can be branched or unbranched, saturated or unsaturated, preferably branched and unsaturated.

Moenomycins are preferably employed as substrates, so that the resulting cleavage products are the substances corresponding to the compound MC, as well as the compounds MB and MA (see formula diagram).

Moenomycinase is activated by metal ions such as Co⁺⁺, Ni⁺⁺, Mn⁺⁺ and Mg⁺⁺ (0.05-1.0 mM). Although greatest activation is seen with Ni⁺⁺, the currently preferred ion for activation of moenomycinase for commercial development is Co⁺⁺ (0.10 mM).

Another enzyme is required for the dephosphorylation of the phosphoglyceric acid lipid, which is obtained by incubation with moenomycinase, of the general formula II in which R¹ is hydrogen, and can also be obtained from the microorganism according to the invention. The inventors have called this enzyme MBase. MBase can likewise be isolated from the microorganism by methods known per se. For example, the cells are disrupted with ultrasound, and the resulting crude extract is further enriched either by ammonium sulfate fractionation (25-55% saturation) or ultracentrifugation. This is followed by dialysis. The moenomycinase and MBase are finally separated by chromatography.

The MBase is increasingly inactivated at temperatures above 37° C. as well as when pH falls in the acid pH range below pH 5.

The cleavage of the moenomycinase, as well as of the phosphoglycolipid antibiotics can, as already mentioned, be carried out with whole cells or enzyme isolates.

The reaction is generally carried out in aqueous medium at a pH of about 5.5-8.5, preferably pH 7-8. The reaction time is generally 5-48 hours, preferably about 24 hours. The reaction temperature can be from 4° to 60° C., preferably 30° to 37° C. The substrate concentration ought to be in the range from 0.1 to 5%, preferably 1 to 2%.

It is still possible to carry out the reaction at temperatures or pH values which are higher or lower than stated. However, the moenomycinase is then less active.

The reaction products resulting from moenomycin A are the substances MB and MC depicted in the diagram. The product MA can be obtained by incubation of MB with MBase at 30° to 37° C., preferably at 35° to 37° C., and pH 5.5 to 8.5, preferably pH 6 to 8, over a period of about 24 hours.

A process for the preparation of MA is described in European Patent Application EP 503419.

The said reaction products can be used as antibiotic (for example MB) or as building blocks for the synthesis of transglycosylase inhibitors (for example MA and MC).

The invention is described in more detail by means of examples. Unless stated otherwise, percentage data relate to weight.

EXAMPLE 1 Maintenance of the Bacillus Spec. DSM 4675 Strain

Bacillus spec. DSM 4675 is maintained on the following solid nutrient medium (medium 1):

    ______________________________________                                         Bacto tryptone (Difco)                                                                            10 g/l                                                      Yeast extract (Difco)                                                                              5 g/l                                                      NaCl                5 g/l                                                      Agar               15 g/l                                                      pH 7.2                                                                         ______________________________________                                    

The medium is distributed over test tubes and sterilized at 121° C. for 30 minutes, then cooled, inoculated with the culture and incubated at 37° C. for 2-3 days.

The grown culture is rinsed off to provide the inoculum for the following, moenomycin-containing main culture (medium 2):

    ______________________________________                                         Corn starch            40    g/l                                               Soybean meal           35    g/l                                               Sucrose                10    g/l                                               CaCO.sub.3             8     g/l                                               Corn steep             4     g/l                                               CoSO.sub.4             20    mg/l                                              ® Genapol (alkyl polyglycol ester                                                                 5     ml/l                                              Moenomycin A           3     g/l (sterile                                                                   filtered)                                         pH 7.6                                                                         ______________________________________                                    

300 ml Erlenmeyer flasks each containing 30 ml of this medium are inoculated and then incubated at 37° C. and 190 rpm for 8-48 hours. Analysis of the culture filtrate by thin-layer chromatography shows that the compounds MA, MB and MC are detectable as cleavage products of moenomycin, and that towards the end of the reaction there has been complete disappearance of the moenomycin employed.

EXAMPLE 2 Preparation of Cell-Free Extracts

To prepare cell-free extracts, Bacillus spec. DSM 4675 is cultured in a fermenter. For this, cells are rinsed off the agar plate to provide a 10 ml inoculum for a preculture (500 ml of medium 2 without Flavomycin in a 2 l Erlenmeyer flask) which is then incubated at 37° C. and 190 rpm for 24 hours.

A 12 l laboratory fermenter containing 9 l of medium 3 is used for the main culture stage:

    ______________________________________                                         Peptone                 12.5   g/l                                             Glycerol                20.0   tg/l                                            Citrate                 2.0    g/l                                             K.sub.2 HPO.sub.4       1.5    g/l                                             MgSO.sub.4 × 7H.sub.2 O                                                                          0.5    g/l                                             FeCl.sub.3 × 6H.sub.2 O                                                                          0.04   g/l                                             Desmophen (propylene glycol)                                                                           5.0    ml/l                                            pH 6.8                                                                         ______________________________________                                    

This is inoculated with 500 ml of preculture and incubated at 37° C., 300 rpm and an aeration rate of 0.5 vvm for 24 hours.

The grown culture is centrifuged, and the cell paste is resuspended in potassium phosphate buffer (pH 7.0) 50 mM (1 g of wet cells+2 ml of buffer). The cells are then disrupted with ultrasound, a French Press® or Dyno Mill®, and the resulting crude extract is used for the conversion.

In a test mixture containing 100 μl of crude extract, 12 mg of moenymycin and 900 μl of potassium phosphate buffer (pH 8.0) 50 mM there is within 7-24 hours at 37° C. 50% breakdown of the substrate employed. The reaction products found are MA, MB and MC.

EXAMPLE 2A Isolation of Moenomycinase

Moenomycinase has been isolated from Bacillus spec. DSM 4675 as follows:

Cells grown as in Example 2 were suspended at a concentration of 1 g cells/2 ml in 20 mM potassium phosphate buffer, pH 8.0, containing 0.1 mM CoCl₂. The suspended cells were sonicated for 20 seconds. After sonication, the suspension was centrifuged for 20 min×20,000 g. The supernatant was discarded and the pellet resuspended in the same buffer to which has been added 1% Triton X-100 and incubated for 1 hr at room temperature with stirring. The suspension was then centrifuged for 2.5 hrs×100,000 g. After such centrifugation, 90-95% of the moenomycinase activity was found in the supernatant.

Moenomycinase solubilized using Triton X-100, as described above, was further purified by (NH₄)₂ SO₄ precipitation. As (NH₄)₂ SO₄ concentration was increased from 0% to 40%, the moenomycinase precipitated at 30-40% and entered a fatty phase that floats above the aqueous phase. The aqueous phase was discarded, and the fatty phase was dissolved in 20 mM Tris HCl buffer, pH 8.0, containing 0.1 mM CoCl₂ and 0.1% Triton X-100.

The dissolved enzyme was further purified by chromatography. For anion exchange chromatography, the enzyme was bound to a column of DEAE-52 (Whatman) or MonoQHR-5-5 (Pharmacia) and then eluted with 0.2-1.0M NaCl. Presence of moenomycinase in the fractions was monitored by measuring the conversion of moenomycin A to MC, as described in Example 3, below. Further purification was achieved using hydrophobic chromatography. The enzyme was bound to phenylsepharose (Pharmacia), and was then eluted with 40% methanol. The enzyme was concentrated by ultrafiltration using an ultrafiltration membrane (Millipore) which retains molecules with molecular weights ≧10,000 Dalton.

The moenomycinase was further purified by molecular sieve chromatography using a Sephacryl S-200HR (Pharmacia). The enzyme was separated in the Sephacryl chromatography column in 20 mM Tris HCl or potassium phosphate buffer, pH 8.0, containing 0.1 mM CoCl₂ and 0.1% Triton X-100 and washed with additional buffer. By comparison with the elution profiles of a series of standard proteins of differing molecular weight, the molecular weight of the moenomycinase was determined to be 230,000±10,000 Dalton. If desired, the purity of the isolated moenomycinase fraction can be checked using SDS gel chromatography.

EXAMPLE 3 Preparative Conversion of Moenomycin A

Preparative conversions are carried out in a 12 l fermenter containing 8.2 l of potassium phosphate buffer (pH 8.0) 50 mM, 800 ml of crude enzyme extract and 100 g of moenomycin A at 37° C. and 100 rpm. The progress of the conversion is followed by TLC. The entire reaction mixture is freeze-dried after 8-48 hours. The moenomycin breakdown is generally 40-60% (UV analysis from the TLC). The resulting reaction products are MA, MB and MC.

EXAMPLE 4 Preparation of the Breakdown Products

100 g of freeze-dried mixture from the enzymatic conversion were taken up in 2 l of water and extracted twice with 2 l of ethyl acetate each time. Centrifugation was necessary for complete phase separation in this case. The combined organic extracts were dried over sodium sulfate, filtered and evaporated to dryness. 0.4 g (0.4%) of a dark brown oil was obtained, and thin-layer chromatography in the system n-butanol/acetic acid/water=3/1/2 on silica gel (Merck 60 F254 aluminum TLC sheets), spraying with molybdatophosphoric acid/cerium(IV) sulfate color reagent (abbreviated to PMS reagent hereinafter), showed that it comprised mainly component MA (Rf value=0.85).

The remaining aqueous phase was then extracted twice with 2 l of n-butanol each time. Once again, centrifugation was necessary for phase separation. The combined butanol phases were then concentrated as far as possible, and the residue was taken up in a little water and finally freeze-dried. 7.4 g (7.4%) of a yellow powder were obtained and were found on examination by thin-layer chromatography (using the abovementioned conditions and the same detection) to comprise mainly the component MB (Rf=0.52).

The aqueous phase from which non-polar substances had been removed in this way was freeze-dried. The amount of residue resulting from this was 76.9 g (76.9% with a total amount of 85%). Thin-layer chromatography showed that this pale yellow powder was composed of a polar main substance, called MC (Rf=0.1), remaining moenomycin A and by-products.

The crude products of components MA, MB and MC obtained in this way were further purified as follows.

EXAMPLE 5 a) Purification of the Breakdown Product MA

400 mg of MA crude product were chromatographed on 120 g of silica gel (Merck 60, 15-40 mcm) which had been adjusted to a pH of 7.5. (The column material had been pretreated in the following way for this purpose: the silica gel was stirred in 500 ml of 2N HCl for one hour, then filtered off with suction and washed to neutrality. The pH was then adjusted to 7.5 with 1N NaOH, and finally washing with 2 l of water and 500 ml of methanol was carried out. The material pretreated in this way was dried and activated at 120° C. overnight.) Chloroform/ethanol=1/1 was used as eluent. The substance was loaded onto the column in 3 ml of solvent mixture, and 216 fractions each of 2.5 ml were collected. Using TLC analysis (TLC plates and detection as in Example 1, solvent system as for column eluent), fractions 115-175 were combined, dried on sodium sulfate and finally evaporated to dryness. 27 mg of spectroscopically pure MA were obtained.

b) Purification of the Breakdown Product MB

3.1 g of MB-containing crude product from the extraction were chromatographed on 500 g of silica gel which had been adjusted to a pH of 7.5 using the process explained in Example 2. Using a medium-pressure chromatography system (MPLC), chloroform/ethanol/water=4/7/1.5 was used for the elution at a flow rate of 10 ml/min and a pressure of 2-5 bar. After a fore-run of 600 ml, 220 fractions each of 10 ml were collected, combining on the basis of the TLC. Besides mixed fractions containing MB, fractions 90-170 yielded 1.28 g of pure MB after evaporation, taking up in water and freeze-drying.

c) Purification of the Breakdown Product MC

2.2 g of polar crude product from the aqueous phase of the extraction were likewise chromatographed under pressure (MPLC). 500 g of silica gel with a pH of 7.5 were employed (process in Example 2), and the eluent used was ethyl acetate/i-propanol/water=4/5/5. The amount to be loaded was suspended in methanol with 15 g of silica gel, the solvent was evaporated off, and the support treated in this way was introduced into a precolumn, and then elution was carried out at a flow rate of 5 ml/min under a pressure of 2-4 bar. A fore-run of 940 ml was followed by fractionation in 250 fractions each of 10 ml. The fractions were tested by thin-layer chromatography in the system ethyl acetate/i-propanol/water=1/1/1 using PMS color reagent and detection of the UV absorption at 254 nm, and were combined. Besides mixed fractions, concentration of fractions 120-190 to the aqueous phase and subsequent freeze-drying revealed 1.3 g of pure MC, which was investigated by spectroscopy.

EXAMPLE 6 Elucidation of the Structures of the products MA and MB Obtained from Moenomycin A by enzymatic Breakdown

(The numbers of the structures relate to the formula diagram on page 19)

The structure deduced for MA was 1a. The assignment of the structure is based on the ¹³ C NMR spectrum of 1a. Reaction of 1a with diazomethane yielded the methyl ester 1b which is characterized by a ¹ H NMR and an EI mass spectrum.

The structure deduced for MB on the basis of ¹³ C and FAB mass spectrum was 2. Hydrogenation of 2 yielded the decahydro derivative 3a which reacted with diazomethane to give 3b, which had already been obtained previously from moenomycin A by another route. It is consistent with the proposed structures that it was possible to convert 2 (MB) enzymatically into 1a (MA).

Description of the Experiments

1a:

¹³ C NMR (100.6 MHz, CD₃ OD): moenocinol moiety: δ =67.5 (C-1), 123.5 (C-2), 141.6 and 141.8 (C-3 and C-7), 32.3 and 32.5 (C-4 and C-5), 126.7 (c-6), 35.9 (C-8), 40.9 (C-9), 30.7 (C-10), 151.1 (C-11), 33.4 (C-12), 122.7 (C-13), 137.3 (C-14), 36.4 (C-15), 27.7 (C-16), 125.3 (C-17), 132.2 (C-18), 25.9 (C-19), 17.8 (C-20), 16.1 (C-21), 109.2 (C-22), 27.3 (C-23 and C-24), 23.8 (C-25).

Glyceric acid moiety: δ =175.9 (C-1), 80.6 (C-2), 64.1 (C-3).

C₂₈ H₄₆ O₄ (446.6)

1b:

1a was converted into the H⁺ form in aqueous solution using ®Dowex 50 (H⁺ form). 1a (H⁺ form, 18.5 mg, 0.04 mmol) was dissolved in methanol (3 ml) and, at 0° C., excess ethereal diazomethane solution was added. The reaction mixture was maintained at 0° C. for 2 h and at 20° C. for 12 h and then evaporated to dryness. Column chromatography (5 g of SiO₂, petroleum ether/ethyl acetate 2:1) yielded 1b (3 mg).

¹ H NMR (80 MHz, CDCl₃): δ =0.96 (s, 6H, CH₃ -23 and CH₃ -24), 1.61 (s, 6H), 1.68 (s, 3H), 1.73 (s, 3H) (4×CH₃), 1.90-2.12 (allyl Hs), 2.62 (broad d, J=7 Hz, CH₂ -12), 3.78 (s, OCH₃), 3.60-4.30 (OCH₂ and OCH signals), 4.62 (broad s, CH₂ -22), 4.87-5.47 (olefinic Hs). --C₂₉ H₄₈ O₄ (460.7), MS: m/z (%) =460 (0.03), 271 (10), 230 (19), 199 (68), 43 (100).

2:

¹³ C NMR (100.6 MHz, D₂ O): moenocinol moiety: δ =68.6 (C-1), 124.5 (C-2), 142.9 (C-3), 34.6 (C-4), 34.0 (C-5, C-10), 128.1 (C-6), 143.6 (C-7), 37.8 (C-8), 44.1 (C-9), 151.4 (C-11), 37.2 (C-12), 123.5 (C-13), 138.3 (C-14), 42.2 (C-15), 29.1 (C-16), 126.9 (C-17), 133.1 (C-18), 28.0 (C-19), 19.9 (C-20), 18.2 (C-21), 111.2 (C-22), 29.7 (C-23, 24), 25.9 (C-25). Glyceric acid moiety: δ =179.0 (C-1), 81.8 (C-2), 68.6 (C-3). --C₂₈ H₄₇ O₇ P (526.7), FAB-MS (matrix: DMSO/glycerol): m/z=615 (M-3H+4Na)⁺, 593 (M-2H+3Na)⁺, 571 (M-H+2Na)⁺, 492, 267, 231, 185, 165, 143, 115.

3a:

2 (14.9 mg, 28.3 μmol) and PtO₂ (4 mg) were stirred in methanol (3 ml) and acetic acid (50 μl) in an H₂ atmosphere under normal conditions for 3 days. The catalyst was filtered off, and evaporation yielded 3a (13.5 mg). --C₂₈ H₅₇ O₇ P (536.7), FAB-MS (matrix: DMSO/glycerol: m/z=625 (M-3H+4Na)⁺, 603 (M-2H+3Na)⁺, 581 (M-H+2Na)⁺, 558 (M-H+Na)⁺, 514, 500, 498, 432, 404, 362, 340, 298, 288, 266, 186, 164, 142, 115, 93.

3b:

3a was treated in aqueous solution with the ion exchanger (Dowex 50, H⁺ form) in order to liberate all acidic groups. The resin was filtered off and then the solution was freeze-dried. 8.5 mg (15.9 μmol) of the sample treated in this way were dissolved in methanol (2 ml). An excess of ethereal diazomethane solution was added at 0° C. The mixture was left to stand at 0° C. for 2 h and at 20° C. for 12 h. Evaporation and column chromatography (5 g of SiO₂, petroleum ether/ethyl acetate 1:1) yielded 3b (4.0 mg).

¹ H NMR (80 20 MHz, CDCl₃): δ =3.75 (s, OCH₃ and 2 d, 3J_(H),P =10 and 12 Hz, P(OCH₃)₂), 3.20-4.40 (OCH₂ and OCH multiplets), --C₁₃ H₆₃ O₇ P (578.8), MS: m/z (%)=563 (0.1, M--CH₃), 519 (1, M--COOCH₃), 452 (1, M--(CH₃ O)₂ P(O)OH), 381 (3, M--C₁₄ H₂₉, breakage of the link between C-8 and C-9 of the 25 perhydromoenocinol moiety), 229 (8, a), 212 (6, b), 127 (20), 57 (100). ##STR5##

EXAMPLE 7 Antibiotic Activities of the Cleavage Products

An agar dilution test with Mueller-Hinton agar was carried out to determine the antibacterial activities (Antibiotics in Laboratory Medicine, V. Lorian, Ed., Baltimore 1986, pages 1-10).

    ______________________________________                                         Minimum inhibitory concentration (μg/ml)                                                  Str.       Staph.                                                              pyogenes   aureus   E. coli                                      Cleavage products                                                                            77         503      DC2                                          ______________________________________                                         MA            >100       >100     >100                                         MB            3.125      25       >100                                         MC            >100       >100     >100                                         ______________________________________                                    

EXAMPLE 8 Transglycosylase Assay

The inhibition of the polymerization of the peptidoglycan-sugar chains by the cleavage products was carried out by the assay described by Izaki (J. Biol. Chem. 243, 3180-3192, 1968) using lipid intermediates from the cell membrane of E. coli K 12.

It emerges from this this moenomycin A (20 μg/ml) inhibits the transglycosylase reaction by 52.7% and the cleavage product MB inhibits the enzyme by 32.9%.

Results of another study of the inhibition of the transglycosylase reaction by moenomycin cleavage products in vitro is shown in the following Table. The values in the Table show the inhibition of peptidoglycan-sugar chain synthesis in vitro. Decahydro MB is an analog of MB that has no double bonds in the alkyl chain.

    ______________________________________                                         Inhibition of In Vitro                                                         Peptidoglycan Synthesis                                                                      Final          %                                                 Compound      Concentration (μg/l)                                                                       Inhibition                                        ______________________________________                                         MB            12.5           94                                                MA            12.5           67                                                Decahydro MB  12.5           28                                                ______________________________________                                    

EXAMPLE 9 Synthesis of a Transglycosylase Inhibitor using MA as Building Block

The first step in the synthesis of a transglycosylase inhibitor using MA as a building block is the synthesis of MA-methylester. A mixture of dried MA (6.0 g) and anhydrous MeOH is stirred at room temperature for 30 hours in the presence of Dowex® 50 WX2 (H⁺ -form). Dowex® 50 WX2 is an ion exchanger which acts as an acid and catalyzes the esterification. After 30 hours, the catalyst is removed by filtration, the solvent is evaporated in vacuo and the remaining residue is further purified by column chromatography [silica gel; elution with hexane:ethylacetate (7:1)] in order to obtain MA-methylester. The yield is 4.1 g (=68%).

The second step is the synthesis of the transglycosylase inhibitor 2-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glycopyranosyl)-4-O-acetyl-3-O-carbamoyl-1-O{[(R)-2-methyloxycarbonyl-2-(3,8,8,11,14,18-hexamethylnonadec-2,6,11,13,17-pentenyloxy)-ethoxyl]hydroxyphosphoryl}-α-D-galactopyranuronamide, triethylammonium salt, using the MA-methylester. To a solution of 1H-1,2,4-triazole (41.3 mg, 0.6 mmol) in 4:1 THF-pyridine (2 ml) is added 1,1,1-trichloro-2-methylprop-2-yl dichlorophosphite (29.6 μl, 0.15 mmol) and the mixture is stirred at 0° C. for 20 min with the formation of a colorless precipitate. A solution of 2-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-β-D-glycopyranosyl)-4-O-(2,2,2-trichlorethoxy)carbonyl-3-O-carbamoyl-α-D-galactopyranuronamide (Moller et al., Tetrahedron, 49:1635-1648 (1993)--compound 6 h), (90 mg, 0.148 mmol) in 4:1 THF-pyridine (2 ml) is added and stirring at 0° C. is continued for 1.5 h. TLC control (hexane-CHCl₃ -methanol 1:1:0.75) indicates a quantitative reaction. A solution of MA-methylester (70 mg, 0.15 mmol) in 4:1 THF-pyridine (1 ml) is added and the reaction mixture is stirred at 0° C. for a further 6 h. Then bis(trimethylsilyl)peroxide (32 μl, 0.15 mmol) is added and the mixture is stirred at 0° C. for 15 h. The solvent is evaporated in a stream of argon until only 0.5 ml of solution remains. This solution is shown to be free of peroxides. Pyridine (5 ml) is added and the stirred solution is treated with Zn-Cu couple (130 mg) and 2,4-pentanedione (100 μl) for 6 h at 20° C. Filtration, solvent evaporation and MPLC (CHCl₃ -methanol 2.5:1) are used for further purification (78.1 mg, 47%).

Protecting groups (e.g., acetyl or methyl groups) are removed by methods well known to a person skilled in the art. The acetyl groups can, for example, be removed as follows:

A solution of the transglycosylase inhibitor (5 mg, 0.0046 mmol) in 2:1 methanol-water (double distilled, 0.5 ml) is flushed with argon and then 0.3 mol/l LiOH (92.0 μl, 0.00276 mmol) is added at 0° C. The mixture is stirred at 0° C. for 30 min. The reaction is stopped by addition of Dowex® 50 WX2 (H⁺ form). Stirring at 20° C. for 30 min, filtration, lyophilization, and liquid chromatography (gradient CHCl₃ -methanol 2:1→CHCl₃ -methanol-water 20:10:1.5) yields the unprotected transglycosylase inhibitor (2.0 mg, 45%).

The methyl group can be removed by the following procedure:

A solution of the transglycosylase inhibitor (20.2 mg, 0.014 mmol) in 2:1 methanol-water (double distilled, 2 ml) is flushed with argon, and then 0.3 mol/l LiOH (371.7 μl, 0.112 mmol) is added at 0° C. The mixture is stirred at 20° C. for 13 h. The reaction is then stopped by addition of Dowex® 50 WX2 (H⁺ form). Stirring at 20° C. for 30 min, filtration, and lyophilization yields a sample of the unprotected transglycosylase inhibitor.

The unprotected inhibitor is then used for the assay. Transglycosylase activity is assayed by the method of Example 8. 

We claim:
 1. The compound of formula II ##STR6## in which R¹ is hydrogen and R² is a branched or unbranched, unsaturated (C₅ to C₅₅)-alkyl group.
 2. The compound as claimed in claim 1, wherein the alkyl group has a chain length of 10 to 30 carbon atoms.
 3. The compound as claimed in claim 1, wherein the alkyl group as a chain length of 20 to 25 carbon atoms.
 4. A compound having the formula ##STR7## 